Electric heaters have been used in various applications for heating, and retaining the heat of, various devices, components, etc. Recently, research has been conducted into the use of an electric heater in a therapeutic method for thermally cauterizing a diseased site, and a thin electric heater usable in such an application is desired. For example, the electrically heated needle disclosed in Patent Literature 1 is configured such that a heating element and a thermocouple are accommodated in a hollow pipe, the distal end of which is blocked by a chip capable of puncturing a living body. The heating element is formed by winding a fine heating wire in a coil-like manner around a core composed of a thread of glass fiber, with the distal side to be inserted into the hollow pipe being half-folded, and the proximal side being connected to a covered electrical wire via a connector.